I still hear people talking a lot of talk about how a harder or lighter tamp will affect the flow rate of a shot. I'd have to disagree from experience. Holding the dose constant I've tamped from 10 to 80 lbs of pressure and still ended up with consistent flow rates. example 18g dose 10lb tamp 27seconds to 2oz. then holding 18g constant tamped up to 80 lbs and still getting to 2oz in 27 seconds +/- 1 second.

I really believe that it's primarily the amount of coffee and the particle size of the grounds that ultimately have the most influence on flow rates. I've even skipped the tamp altogether expecting a gusher, but surprise... still poured near 25 or so seconds. Didn't taste that good... much different flavour profile; puck looked like it was tamped though... The pressurized water is tamping the puck harder than most of us will ever be able to anyhow.

I think that different tamping pressures could possibly change some of the dynamics of the extraction within the puck... ideas anyone? I think I may have noticed that blonding & thinning strands occurred sooner when tamping with excessive force (60 lbs +).

would like to get some feedback and see if anyone has other evidence to the contrary, or just other insights...

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worms coming out of the can now.

Jared Rutledge said:
i think the general idea behind a standard tamping pressure is to ensure that all your baristi are regulating their doses. in other words, if you keep your espresso bean consistent, and know your 18g dose sits right at the ridge line on a portafilter basket with your standard 30lb tamp, then you will likely pull more consistent shots.

of course (as has been determined) tamp pressure between 10lb-80lb isn't a huge determiner of the espresso's taste. i've just always viewed it as a tool to keep everything consistent.

as a side note, i would imagine most people are tapping the portafilter during dosing to ensure the espresso settles? i usually do it on the top of the dosing chamber itself but i saw Gwilym Davies do it on the dosing fork at the WBC this year. that's one major factor i learned in sydney that helped my espresso go from shaky to good.

Tamp could be directly related to how quickly the grinds absorb H20. A puck that isn't tamped will likely let the initial burst of water (pre-infusion or not) reach the dry grounds on the bottom of your puck more quickly than if you had tamped 100lbs. But because the grinds are absorbing the coffee, you don't see a shot start any earlier. I don't know, just a theory.
Jared Rutledge said:
as a side note, i would imagine most people are tapping the portafilter during dosing to ensure the espresso settles? i usually do it on the top of the dosing chamber itself but i saw Gwilym Davies do it on the dosing fork at the WBC this year. that's one major factor i learned in sydney that helped my espresso go from shaky to good.

The benefit of settling in the forks (if you still got 'em) is that you're limited to how far you can move the PF, so your "thump" is more consistent. Picked up that tip from a very similar discussion here about a year ago...
I have found that a uneven or non-level tamp makes much more of a difference to shot timing than the the weight of the tamp. Perhaps when you try to tamp as hard as you can you don't have as much control and as a result your tamp is uneven. Possibly causing channeling. Not sure though, not an expert by any means.
I would love to see a Vimeo video on the actual experiment.

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